1. Field of the Invention
The invention relates to a method of producing packaging, the packaging surface being coated with a polyelectrolyte complex, and the polyelectrolyte complex being composed of at least one first polymer and at least one second polymer, the first polymer being an anionic polymer, and the second polymer being a cationic polymer. The packaging is distinguished by good fat barrier properties.
When packaging oily or fatty products it is important that the packaging materials used have a high resistance to penetration by fats and oils, or good fat barrier properties. There are a variety of known methods suitable for endowing packaging materials, especially those based on paper or card with resistance to penetration by fats and oils. For this purpose the materials may be coated or impregnated, for example, with solutions or aqueous dispersions of natural or synthetic polymers, paraffins, waxes or fluorinated hydrocarbons. The coating or impregnating compositions in question include, for example, solutions of starches and starch derivatives, galactomannans, carboxymethylcelluloses, polyvinyl alcohols or solutions of other synthetic polymers, such as anionic polyacrylamides, for example. The level of greaseproofing possessed by paper produced by such a method is low. Also known are methods whereby the paper, inside or outside the paper machine, is coated or impregnated with aqueous dispersions of polymers, paraffins or waxes. Known additionally are methods whereby high resistances to penetration by fats and oils are imparted to papers by extrusion coating using melts of polymers, hotmelts, waxes or paraffins.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
EP 1498544 discloses coatings based on polymer emulsions for cellulose substrates with barrier properties. The polymers are ethylene-vinyl acetate copolymers (EVA). US 2007092718 discloses a method of improving the fat and/or water resistance of materials, where the material is treated with wax and polyvinyl alcohol. DE 10 2005 007 483 discloses aqueous dispersions of predominantly anionically charged polyelectrolyte complexes.
Fat barrier coatings with polymer-based films frequently lack sufficient flexibility. In that case, when creasing or folding, in the region of fold sites, e.g. edges or corners of folding boxes or cartons, there may be damage to the barrier film and consequently insufficient fat barrier effects.